Methods and devices for suction transporting with a modulation of the stream of the above mentioned general art, disclose, for example in U.S. Pat. Nos. 5,201,877 and 5,593,252. The modulation of the parameters of the stream during suction transporting performed in these references is very efficient method in order to improve the process of suction of various materials from the surface to be cleaned. In this process, the most efficient frequency and characteristic of the modulation is given in a fixed manner with consideration of mechanical characteristics, the structure of the surface to be cleaned and the material to be transported, and the power of the suction device as well as a structure of its suction element.
In this method, the necessity to provide a required movability of suction with a permitted force for its displacement during a contact of the inlet of a suction line with a surface to be cleaned is taken into consideration. In the known method the fixed, predetermined maximal frequency of modulation of the stream parameters does not change during the process of suction in the zone of cleaning in dependence of a distance between the inlet and the surface to be cleaned. This fact limits the efficiency of the suction device in the process when the inlet approaches the surface to be cleaned, which is connected with a possible preliminary "tensioning" by the suction action and a low-frequency swinging (beating out) of the surface, as well as the material on it to be sucked.
In some cases during action on the structured (porous), uneven or movable surface to be cleaned it is necessary to provide a dynamic change of the frequency and characteristic of modulation of the suction stream parameters, with consideration of the changing rarification in the zone of the inlet when it passes a geometrically predetermined cleaning zone above the surface to be cleaned. It is important for example during vacuum cleaning of corner zones of the surface, curtains, clothing and other soft and movable surfaces, and also in the event of the use surgical medical suction instruments which act on thin, movable film surfaces, mucus, loosened fat zone, during neuro-surgical operations, etc.
Moreover, the provision of the constant high-frequency modulation of suction stream parameters even before entry of the inlet in the zone of a possible contact with the surface to be cleaned also limits in many cases the possibility of efficient and safe utilization of various devices for the known modulation method. Examples of this situation are various surgical medical suction instruments and devices for suction transporting of various media (plasma, fat, mucus, saliva, etc.) from local inner zones to be operated. Known devices in which the above described method of suction transporting with the stream modulation is performed do not provide for a possibility of automatic turning on (start) of modulation only when the inlet enters the geometrically predetermined cleaning zone, as well as automatic adaptive change (increase) of frequency of modulation when the inlet passes the zone in direction of the surface to be cleaned to a complete contact of the inlet with the surface.
These disadvantages substantially reduce the efficiency and limit the applications of the known methods and devices for suction transporting with a fixed modulation of the stream parameters.